7.1 The Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) (Annex 16) and the Guidelines for Implementing the Policy on Off-site Ecological Mitigation Measures require that mitigation of ecological impacts be sought in the following order of priority: (1) avoid, (2) minimise, (3) compensate on-site and (4) compensate off-site. At each stage, residual impacts should be re-assessed to determine whether there is a need to proceed to the next stage of mitigation. As presented in the EIA report, mitigation measures would be required only for the impacts on uncommon tree species and on subtidal ecology during construction phase. The major concern in subtidal ecology, i.e. the coral communities, is indeed of low conservation value. The coral species found were common and widely distributed in Hong Kong, the colonies were small in size, and the total coverage of coral was very low (< 5%). Moreover, the coral colonies were located further away from the dredging site than the Fish Culture Zone was, in which the increase of suspended solid would be acceptable. No impacts from the suspended solid increase on corals are anticipated. Due to the limited scale of the project and the minor degree of impacts caused, no ecological monitoring would be required. The proposed water quality monitoring station at the Fish Culture Zone (W2) would serve as a checkpoint to detect any unpredicted water quality impacts arising from the proposed project.
7.2 The uncommon tree species should be labelled and probably fenced to avoid direct or indirect disturbance during construction. Works areas should avoid woodland habitats, in particular where these trees are located.
7.3 Construction and maintenance of site runoff control measures would be required at all work sites during construction. These should include barriers to direct runoff to sand/silt removal facilities (sand/silt/traps and/or sediment basins); minimisation of earthworks during rainy season (May to September); and coverage of sand/fill piles and exposed earth during storms.
7.4 Special attention should be paid during the breeding season of Romer’s Tree Frog (March to September) to ensure their habitat landward to Pumping Station P2 site is well protected from site runoff. Barriers should be deployed completely along the landward side of the pumping station site boundary to prevent any site runoff from entering the tree frog habitat. Intactness of the barriers should be frequently inspected.
7.5 Construction and maintenance of site runoff control measures would be required at all work sites during construction. These should include barriers to direct runoff to sand/silt removal facilities (sand/silt/traps and/or sediment basins); use of silt curtains along coastline; minimisation of earthworks during rainy season (May to September); and coverage of sand/fill piles and exposed earth during storms.
7.6 To reduce impacts of sediment resuspension upon nearby habitats and organisms during dredging, all dredging should be done using a closed-grab dredger, and silt curtains should be deployed around the dredger during all dredging activity.
7.7 The implementation schedule of mitigation measures is presented in Appendix A.